Jack and his crew surely go to find that tape Jesse made putting the sister in danger. I think Walt gets mad at Jack and his crew and will try to kill them? Hence the guns in the truck of the car. The ricin could be for Jesse, but I think more for that lady who drinks tea.
Walt will kill Jack and crew as revenge for killing Hank. Jesse will cause an explosion in the lab that kills Todd and Lydia. Marie will commit suicide. The ricin is to kill Saul so he can’t implicate Skyler.